Ozonated water flow and concentration control apparatus and method

ABSTRACT

The invention features an apparatus and a method for supplying ozonated water to more than one process tool. Ozonated water of a first concentration received from an ozonated water generator and water received from a source are mixed to produce ozonated water of a second concentration. The ozonated water of a second concentration is supplied to a first process tool. Ozonated water from the ozonated water generator is supplied to a second process tool while supplying the ozonated water of the second concentration to the first process tool.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application is a continuation-in-part of U.S. patentapplication Ser. No. 09/653,506, filed Sep. 1, 2000, the entiredisclosure of which is incorporated herein by reference.

TECHNICAL FIELD

[0002] The invention relates generally to manufacturing of semiconductordevices and more particularly to the control of ozonated deionized watersupplied to semiconductor processing tools.

BACKGROUND OF THE INVENTION

[0003] Use of ozonated deionized water in semiconductor manufacturingcan provide relatively simple, safe processing steps, such as wafersurface cleaning, passivation, native oxide removal, and removal ofphotoresist.

[0004] Ozonated deionized water generators generally produced ozonatedwater through use of contactors that permit diffusion of ozone from agas into deionized water. Membrane contactors use an ozone permeablemembrane to provide physical separation between liquid and gas, whilepacked column contactors provide intimate mixing of liquid and gas,under pressure to enable higher ozone concentrations.

[0005] A semiconductor fabrication facility often has multiple toolsthat require ozonated water. Different tools can require different ozoneconcentrations and flow rates. The purchase, operation and maintenanceof multiple ozonated water generators can increase manufacturing costsand line shut-downs.

[0006] It would be beneficial to have a less expensive, more reliable,more flexible and more rapidly responsive ozonated water source.

SUMMARY OF THE INVENTION

[0007] The present invention relates to an ozonated water control unitfor use in an improved ozonated water supply system. The control unitcan modify the flow rate and/or concentration of ozonated water receivedfrom an ozonated water generator, for subsequent delivery to a processtool. One or more control units can be used with a single generator tosupply more than one tool with individualized ozonated water needs.

[0008] In various embodiments, the ozonated water supply system cansimultaneously supply ozonated water of different ozone concentrationsto different process tools, even if the system includes only oneozonated water generator. Use of one or more control units with as fewas one ozonated water generator permits independent control of ozonatedwater supplied to two or more process tools.

[0009] Each control unit controls its output flow rate and/orconcentration of ozonated water. Thus, the parameters of the suppliedozonated water can be tailored for each process tool. In one embodiment,the system can supply low ozone concentration ozonated deionized water,for example, for a cleaning process, and simultaneously supply higherozone concentration ozonated deionized water, for example, for astripping process.

[0010] Thus, in a first aspect, the invention features a method ofsupplying ozonated water to more than one process tool. Ozonated waterof a first concentration received from an ozonated water generator andwater received from a source are mixed to produce ozonated water of asecond concentration. Ozonated water of the second concentration issupplied to a first process tool, and ozonated water from the ozonatedwater generator is supplied to a second process tool.

[0011] In a second aspect, the invention features another method ofsupplying ozonated water to more than one process tool. The methodincludes providing an ozonated water control unit. The ozonated watercontrol unit includes an ozonated water input line for receivingozonated water of a first concentration from an ozonated water generatorand a water input line for receiving water from a source. The unit alsoincludes an ozonated water output line in fluid communication with theozonated water input line and the water input line. A valve controls aflow rate of water in the water input line to produce ozonated water ofa second concentration in the output line, in cooperation with a flowrate of ozonated water in the ozonated water input line.

[0012] The method further includes supplying ozonated water of thesecond concentration from the output line to a first process tool andsupplying ozonated water from the ozonated water generator to a secondprocess tool.

[0013] In a third aspect, the invention features an ozonated watercontrol unit. The control unit includes an ozonated water input line forreceiving ozonated water from an ozonated water generator, a water inputline for receiving water from a source and an ozonated water output linein fluid communication with the ozonated water input line and the waterinput line. The unit also includes a valve for controlling a flow rateof water in the water input line to produce ozonated water of a secondconcentration in the output line, in cooperation with a flow rate ofozonated water in the ozonated water input line.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The invention, in accordance with preferred and exemplaryembodiments, together with further advantages thereof, is moreparticularly described in the following detailed description, taken inconjunction with the accompanying drawings.

[0015] In the drawings, like reference characters generally refer to thesame parts throughout the different views. Also, the drawings are notnecessarily to scale, emphasis instead generally being placed uponillustrating principles of the invention.

[0016]FIG. 1 is a block diagram of an embodiment of the relationshipbetween an ozonated water generator and other components utilized insemiconductor manufacturing.

[0017]FIG. 2 is a block diagram of an embodiment of an ozonated watergenerator.

[0018]FIG. 3 is a block diagram of an embodiment of an ozone generatormodule.

[0019]FIG. 4 is a block diagram of an embodiment of a contactor modulecomprising a membrane contactor.

[0020]FIG. 5 is a block diagram of an embodiment of a contactor modulecomprising a packed column contactor.

[0021]FIG. 6 is a block diagram of an embodiment of a contactor modulecomprising more than one contactor.

[0022]FIG. 7 is a block diagram of an embodiment of a portion of acontactor module.

[0023]FIG. 8 is a block diagram of an embodiment of a portion of acontactor module.

[0024]FIG. 9 is a cross-section of an embodiment of a packed columncontactor.

[0025]FIG. 10 is a block diagram of an embodiment of an ozonedestruction module.

[0026]FIG. 11 is a graph of ozone concentration versus time in ozonateddeionized water output from a contactor.

[0027]FIG. 12 is a block diagram of an embodiment of a contactor.

[0028]FIG. 13a is a prior art wet bath.

[0029]FIG. 13b is an embodiment of a wet bath system comprising thecontactor of FIG. 12.

[0030]FIG. 14 is block diagram of an embodiment of an ozonated watercontrol unit.

[0031]FIG. 15 is a block diagram of an embodiment of multiple ozonatedwater control units, an ozonated water generator, a pure water sourceand three process tools.

[0032]FIG. 16 is a block diagram of an embodiment of an ozonated watergenerator and a control unit delivering ozonated water to two processtools.

[0033]FIG. 17 is a detailed block diagram of an embodiment of a ozonatedwater control unit.

DETAILED DESCRIPTION

[0034] In highly simplified form, FIG. 1 shows an embodiment of anozonated water generator 1000 in physical relationship to othercomponents utilized in semiconductor manufacturing. The ozonated watergenerator 1000 receives deionized water (“DI water”) for a DI watersupply 20, oxygen (“O2”) from an oxygen gas supply 30, and suppliesozonated deionized water (“DIO3”) to one or more semiconductor processtools 40. Used or excess DI water or DIO3 can be dumped via drain lines50. In one aspect, the invention provides an ozonated water generatorwith improved control, lower cost, and improved reliability.

[0035] In a more detailed embodiment, the block diagram of FIG. 2depicts representative modules of the ozonated water generator 10 andrelated components contained within a cabinet 1020. For clarity,electrical and air pressure control components of the ozonated watergenerator 10 are not shown.

[0036] An ozone (“O3”) generator module 800 generates O3 from oxygendelivered by a O2 line 813. A carbon dioxide (“CO2”) line supplies CO2for use by the module 800. Cooling water is supplied to the O3 generatormodule 800 by a cooling water input line 812 and removed via a coolingwater outlet line 811. The O3 generator produces O3, typically mixedwith CO2 and O2. Some O2 remains since the conversion to O3 is less than100% efficient while CO2 is optionally added depending on user needs.This dry gas mixture is delivered to a contactor module 100 via a drygas line 815.

[0037] The contactor module 100 produces DIO3 from DI water supplied viaa DI water line 112 and O3 received via the dry gas line 815. The DIO3generally comprises DI water and O3, O2, and CO2 dissolved in the DIwater. The DIO3 is directed toward the semiconductor tools 40 via a DIO3line 115.

[0038] As will be discussed below with reference to FIGS. 4, 5, and 6,in various embodiments of the contactor module 100, the contactor module100 comprises one or more contractors 110, 120 of varying type. The useof a O3/CO2 gas mixture is optional in the DIO3 generation process,serving in part to stabilize the concentration of O3 in ozonated DIwater.

[0039] A pressure relief drain line 113 carries water emitted by thecontactor module 100 in response to excessive water pressure (describedin detail below). Water from the pressure relief drain line 113 isdeposited into a drip pan 1040. The drip pan 1040 is also positioned tocapture water leaks from the contact module. Liquid may be removed fromthe drip pan 1040 via a cabinet drain 1045.

[0040] A water dump line 114 carries excess DI water or DIO3 to a drainexternal to the ozonated water generator 1000. Used DIO3 water from thesemiconductor tools 40 can be returned to the ozonated water generator1000 via a DIO3 return line 41, a flow meter 11 and a flow rate controlvalve 12. This permits the ozonated water generator 1000 to providecomplete monitoring and control of the use of DIO3 by the semiconductortools 40.

[0041] The contactor module 100 typically produces a humid gascomprising O2, H2O, O3, and CO2 as an exhaust product of the productionof DIO3. The humid gas is directed along the humid gas line 911 to theozone destruction module 900. The destruction module 900 substantiallyeliminates ozone from the humid gas prior to exhaust of the humid gasalong gas exhaust line 912. This process protects the environment andsemiconductor processing workers from the potentially harmful presenceof ozone. As an additional safety precaution, the cabinet 1020 isequipped with a gas leak detector 1030, i.e. a cabinet “sniffer”, tomonitor for ozone gas leaks within the cabinet 1020.

[0042] For simplicity in the following descriptions, controlling andmonitoring elements related to gas and liquid lines are given commonnumerical identifiers in FIGS. 3-10. These control and monitoringelements include: volume flow rate meters 11; volume flow rate controlvalves 12; on/off valves 13; pressure regulators 14; filters 15 (forparticulates or condensate); check valves 16; pressure relief valves 17;sample valves 18; flow rate restrictors 19; ozone concentration monitors20; condensation monitors 21; and temperature gauges 22. These elementsare illustrative and not comprehensive. Control and monitoring elementsare shown in the Figures primarily for illustrative purposes. Thenumber, type and placement of such elements can be varied with the needsof different embodiments.

[0043] It should further be understood that gas and liquid lines areconstructed of appropriately selected materials. Dry gas lines and DIwater lines can be comprised of stainless steel. Lines carrying liquidor humid gas that contains ozone are typically comprised of afluoropolymer.

[0044]FIG. 3 shows a block diagram of an embodiment of the ozonegenerator module 800 in greater detail. An ozone generator 810 receivesoxygen from the O2 line 813 via an on/off valve 13 and a pressureregulator 14 and converts the O2 into O3. CO2 can also be delivered tothe ozone generator 810 via the CO2 gas line 814, pressure regulator 14,volume flow rate control valve 12 and flow rate restrictor 19. Further,CO2 can be added to gas after it exits the ozone generator 810 viavolume flow rate control valve 12 and check valve 16. The check valve 16blocks back-flow of gas into the CO2 delivery lines.

[0045] In one embodiment, the ozone generator 810 utilizes a dielectricbarrier discharge to produce dry ozone. The ozone concentration dependson the volume flow rate through the discharge as well as the power,pressure and temperature of the discharge.

[0046] Addition of CO2 to the O2 prior to entry into the ozone generator810 provides a dopant for the O3 creation process. It protects againstlong term deterioration of performance of the ozone generator 810 due tooxidation of a power electrode. Alternative dopants can be used, such asN2 or CO. Additional CO2 can be added to the dry gas that exits theozone generator 810. CO2 has the additional advantage of stabilizing O3concentrations.

[0047] Use of CO2 has other advantages. Use of N2 creates the risk ofnitric oxide formation during discharge. This can lead to chromiumcontaminants even in the presence of electropolished stainless steeltubes.

[0048] Large amounts of CO2 are required for stabilization of ozone inDIO3. The half-life governing the decay of ozone is a function of thequality of the DI water. Preferably, this quality should provide ahalf-life of about 15 minutes. N2, too, can affect stability of ozone,along with the presence of CO2. While high purity CO2 and O2 arepreferred, as an alternative, low purity O2, with inherent N2contamination, can be used, taking advantage of the N2 impurity as adopant. Typically, N2 of about 50 to 100 ppm or CO2 of about 100 to 500ppm is required for stabilization. CO2, however, is typically requiredfor enhancement of short-term stability. Hence, CO2 is typically addedto the gas both before and after entry into the ozone generator 810.

[0049] The resulting dry gas can be sampled via sample valve 18, todetermine the concentrations of O3, O2 and CO2. The dry gas then passesto the dry gas line 815 via filter 15, volume flow rate control valve12, check valve 16, filter 15, and on/off valve 13.

[0050] The ozone generator module 800 is also provided with coolingwater via the cooling water input line 812 and the cooling water outputline 811. The cooling water is delivered to the ozone generator 810 viaon/off valve 13, filter 15, volume flow rate control valve 12 and volumeflow rate meter 11. After exiting the ozone generator, the cooling waterpasses through on/off valve 13.

[0051]FIGS. 4 through 8 show various embodiments of the contactor module100. The contactor module 100 generally includes one or more contactorsof various types. For example, different types of counter-currentcontactors can advantageously be employed. In counter-currentcontactors, gas and water move in opposite directions through thecontactor.

[0052] Contactors of the counter-current type have further variants.Membrane contactors utilize a hydrophobic membrane to separate gas andliquid within the contactor. Typically, dry gas enters the top of themembrane contactor and exits the bottom, while DI water enters at thebottom and DIO3 exits at the top. Packed contactors in contrast utilizedirect contact between gas and liquid, with a packing material used toslow transit through the contactor. Typically, DI water enters at thetop while the dry gas enters at the bottom. The packing materialincreases the duration of contact between gas and liquid. The packingmaterial can comprise, for example, fluoropolymer, quartz, or sapphire.

[0053] Since gas and liquid are separated by a membrane in a membranecontactor, pressure differences between the gas and the liquid canexist. Further, the inlet DI water volume flow rate is coupled to theoutlet DIO3 volume flow rate. Conversely, liquid and gas pressures areequal in packed column contactors and the inlet and outlet volume flowrates are decoupled. Hence, for short periods, the inlet and outletvolume flow rates can differ. In part due to these differences, membranecontactors have a relatively low maximum volume flow rate though goodcontrollability, while packed column contactors typically have a greatermaximum volume flow rate though with poorer controllability.

[0054] During interaction of liquid and gas, ozone in the gas dissolvesin the liquid. Generally, the ozone concentration in the liquid, atequilibrium, will be proportional to the partial pressure of ozone inthe gas. In the case of a packed contactor, for example, the contactortypically operates under pressure to provide the potential for higherozone concentration DIO3 output. Time of contact between liquid and gaswill also affect the ozone concentration in liquid exiting thecontactor. For a one yard tall packed contactor, typical duration ofliquid passage through the contactor is about 5 to 10 seconds.

[0055] As shown in FIG. 4, the contactor module comprises a membranecontactor 110. The lower portion of the contactor 110 receives DI waterfrom the DI water line 112 via volume flow rate control valve 12. In theevent of excess inlet water pressure, a pressure relief valve 17 canrelease a portion of DI water to the pressure relief drain line 113.After processing within the contractor 110, the DIO3 leaves the upperportion of the contactor 110 via a volume flow rate meter 11 and isdirected to the DIO3 line 115 via an on/off valve 13.

[0056] Excess or unneeded DIO3 exiting the contactor 110 can be directedto the water dump line 114 via an ozone monitor 20, an on/off valve 13,a volume flow rate meter 11, and a volume flow rate control valve 12.

[0057] The upper portion of the contactor 110 receives the ozonecontaining dry gas from the dry gas line 815 via an on/off valve 13.Humid gas exists the lower portion of the contactor 110 and is directedto the humid gas line 911 via a volume flow rate meter 11. Subsequently,the ozone destruction module 900 removes ozone from the humid gas.

[0058]FIG. 10 shows an embodiment of the ozone destruction module 900 inmore detail. An ozone destructor 910 receives humid gas from the humidgas line via a volume flow rate control valve 12, an on/off valve 13, afilter 15 and a condensate monitor 21. The humid gas can be sampled viaa sample valve 18.

[0059] The ozone destructor 910 reduces ozone concentration in the humidgas via use of a catalyst. Exhaust gas from the ozone destructor 910 isdirected to the exhaust gas line 912 via a temperature gauge 22 and avolume flow rate monitor 11. Generally, the efficiency of ozonedestruction is assumed to be adequate as long as the temperature,monitored via the temperature gauge 22, remains above a minimum level.

[0060]FIG. 5 shows another detailed embodiment of the contactor module1001. In this embodiment, the contactor module 100 comprises a contactor120 of the packed column type. The upper portion of the contactor 120receives DI water from the DI water line 112 via volume flow ratecontrol valve 12. After processing within the contractor 120, the DIO3leaves the lower portion of the contactor 120 via a volume flow ratemeter 11 and is directed to the DIO3 line 115 via an on/off valve 13.

[0061] Excess or unneeded DIO3 exiting the contactor 120 can be directedto the water dump line 114 via an ozone monitor 20, an on/off valve 13,a volume flow rate meter 11, and a volume flow rate control valve 12. Inthe event of excess water pressure within the contactor 120, a pressurerelief valve 17 can release a portion of water residing in the lowerportion of the contactor 120 to the pressure relief drain line 113.

[0062] The lower portion of the contactor 10 receives the ozonecontaining dry gas from the dry gas line 815 via an on/off valve 13.Humid gas exits the upper portion of the contactor 120 and is directedto the humid gas line 911 via a volume flow rate meter 11. Subsequently,the ozone destruction module 900 removes ozone from the humid gas.

[0063] The embodiment depicted in FIG. 5 further provides for monitoringof liquid level in the contactor 120 through a liquid level sensor 150that is in fluid communication with the contactor 120. Liquid level ismeasured via a capacitive gauge 152. Further, if the liquid level dropsbelow a lowest permissible level, as sensed via a light barrier 153, theon/off valve 13 is closed to prevent further removal of liquid. If thelevel rises above a highest permissible level, as sensed by anotherlight barrier 151, another on/off valve (not shown) is closed to preventfurther entry of DI water into the contactor 120. In either case, analarm is given as notice of the problem condition.

[0064]FIG. 6 shows an embodiment of a contactor module 100 that employstwo contactors 120 operating in parallel. For clarity, components of theembodiment of FIG. 6 that are comparable to those in FIG. 5 are notshown. Use of two or more contactors 120 in parallel has severaladvantages, including larger possible flow rates of DIO3 and continuedproduction of DIO3 in the event that one of the contactors 120 fails.Further manufacturing and operation of two relatively small contactors120 can be less costly than a single relatively large contactor 120. Inanother embodiment, two or more contactors 120 are operated in series toprovide higher possible ozone concentrations in the DIO3.

[0065]FIG. 7 shows a portion of a further embodiment of a contactormodule 100 that is related, in part, to the embodiment of FIG. 5. Forclarity, components of the embodiment of FIG. 7 that are comparable tothose in FIG. 5 are not shown. The embodiment is shown with a packedcolumn contactor 120, however, a variety of contactor types can beemployed in conjunction with the principles utilized in this embodiment.

[0066] A portion of DI water received from the DI water line 112 isdiverted by a DI water bypass line 610. Alternatively, a second DI waterline (not shown) could supply the DI water bypass line 610.

[0067] After passing a volume flow rate meter and a volume flow ratecontrol valve, DI water in the DI water bypass line 610 is mixed withDIO3 exiting the contactor 120. DIO3 derived from this mixture isdirected towards the semiconductor tools via the DIO3 supply line 115.By adjusting the flow rate of DI water in the bypass line 610, the ozoneconcentration and flow rate of DIO3 in the DIO3 line can be varied.

[0068] A number of advantages arise from the use of the bypass line 610.Typically, prior art ozonated water generators produce ozoneconcentration transients in DIO3 when implementing a demand for a changein concentration. Changing the flow rate of DI water or dry gas enteringa contactor to change ozone concentration leads to a period of timeduring which conditions within the contactor transition to a newsteady-state. This effect is illustrated by the graph shown in FIG. 11.

[0069] For example, by decreasing the flow rate of DIO3 exiting acontactor, the concentration of ozone in the DIO3 can be increased.Decreasing the flow rate can be used to increase time span that waterspends within the contactor 110, 120. This permits greater duration ofinteraction between the water and ozone within the gas. There is a timedelay, however, during which DIO3 exiting the contactor has not spentthe full, increased time span within the contactor. Hence, the ozone inexiting DIO3 gradually increases to the new, desired level. Further,ringing or oscillations in concentration, as illustrated qualitativelyin FIG. 11, can be superimposed on the gradually increasing ozoneconcentration.

[0070] These effects are generally undesirable in semiconductorprocessing. Users of DIO3 often wish to make immediate, stableadjustments in concentration level. By adjusting the flow rate of DIwater in the bypass line 610, relatively immediate and stable changes inozone concentration in DIO3 delivered to the DIO3 line 115 can beachieved. Excess DIO3 beyond that required by the semiconductor tools 40can be directed to the water dump line 114.

[0071] Using the above approach, a constant flow rate of water in thecontactor 110, 120 can be maintained to maintain a stable ozoneconcentration in DIO3 exiting the contactor 110, 120. This very stablesupply of DIO3 can then mixed with DI water of a variable flow rate toachieve desired changes in concentration in DIO3 delivered to the DIO3line 114. In a related embodiment, a constant, low flow rate of water ismaintained in the contactor 110, 120 at all times, even when DIO3 demandfrom the semiconductor tools is zero. With a constant flow, DIO3 isnearly immediately available. Further, with a relatively low flow ratein the contactor, relatively little volume flow of DIO3 need be dumpedwhen no DIO3 is needed. At these times, DI water flowing through thebypass line 610 can be reduced or shut off to further conserve water.

[0072] As an example of the above method, the contactor 120 can beoperated at a constant flow rate of 5 l/min (liters per minute) with anexit DIO3 ozone concentration of 80 ppm. Mixing a 15 l/min flow rate ofDI water from the bypass line 610 with this contactor 120 output willyield DIO3 of 20 ppm at a flow rate of 20 l/min in the DIO3 line 114.The full 20 l/min of DIO3 at 20 ppm concentration can be utilized by thesemiconductor tools 40, or a portion can be dumped.

[0073] Further benefits can accrue through use of the above method. Asone example, maintaining water flow in the contactor 110, 120 or in thebypass line 610 can reduce bacterial growth. For example, DI water flowcan be maintained in the bypass line 610 to provide continuous flow inthe bypass line 610 and other DI water carrying lines to protect theselines against bacterial growth. As another example, changes in liquidflow rates through a contactor 110, 120 can cause pressure spikesleading to failure of the contactor 110, 120. Use of the above method toreduce or eliminate these flow rate changes can thus increase contactor110, 120 reliability.

[0074]FIG. 8 shows a portion of a further embodiment of a contactormodule 100 that is related, in part, to the embodiment of FIG. 5. Forclarity, components of the embodiment of FIG. 8 that are comparable tothose in FIG. 5 are not shown. The embodiment is shown with a packedcolumn contactor 120, however, a variety of contactor types can beemployed in conjunction with the principles utilized in this embodiment.

[0075] After exiting the contactor 120 and passing a volume flow ratemeter, a portion of DIO3 can be diverted via a recirculation line 180 toagain enter the contactor 120, optionally via a reservoir 710. Thoughnot shown, a water pump can be included to urge the DIO3 towards thecontactor 120. The reservoir, in part, provides buffering, i.e. storage,of diverted DIO3 to permit greater control over recirculation ofdiverted DIO3.

[0076] The diverted DIO3 can reenter the contactor 120 via a liquid lineconnector used for DI water received from the DI water line 112.Alternatively, the contactor 120 can include a separate connector forthe diverted DIO3 to reenter the contactor 120.

[0077] With recirculation of diverted DIO3 through the contactor, DIO3of increased ozone concentration can be obtained. This providesadvantages over prior art ozonated water generators. For example, higherozone concentration DIO3 can be produced in comparison to priorgenerators that incorporate a comparable contactor. Further, a smaller,less expensive contactor can be employed to produce DIO3 of a desiredozone concentration level.

[0078] With reference to the cross-sectional view of FIG. 9, an improvedpacked column contactor 500 is now described. The contactor 500 can beadvantageously employed in various embodiments of the contactor module100, such as those described above.

[0079] The contactor 500 comprises a liquid and gas interaction vesselwithin which elevated pressures are maintained during operation of thecontactor 500. The vessel comprises a first end portion 510 and a secondend portion 520. As shown in FIG. 9, the vessel further comprises acentral portion 530. The first end portion 510 is joined to a first endof the central portion 530 while the second end portion 520 is joined toa second end of the central portion 530, to provide a substantiallyliquid and gas tight liquid and gas interaction vessel. Within thevessel are packing restraints 560 and packing material (not shown).

[0080] The portions 510, 520, 530 are preferably formed from a polymerthat comprises a fluoropolymer. The fluoropolymer is selected from agroup comprising pertetrafluoroethylene, perfluoroalcoxy,polyvinlydifluoride, and fluoroethylenepropylene. Generally, materialswith ozone resistance can be considered for use in forming the portions510, 520, 530. The portions 510, 520, 530 can be manufactured by variousmeans. For example, some fluoropolymers, such as perfluoroalcoxy, areamenable to injection molding. Other, such as pertetrafluoroethylene,can be machined.

[0081] A sufficient wall thickness of the portions 510, 520, 530 ischosen to provide self-supporting mechanical stability duringpressurized operation of the contactor. Hence, unlike prior art packedcolumn contactors, the contactor 500 requires no stainless steelhousing.

[0082] Assuming a cylindrical shaped vessel, a sufficient wall thicknesscan be calculated through use of the following equations:

t=r(P/σ_(max));

σ_(max)=(1/s)σ_(y);

[0083] where t is the required wall thickness, r is the internal radiusof the vessel, P is the internal pressure, σ_(max) is the maximumallowable tensile wall stress, σ_(y) is the yield strength for theparticular material used to form the vessel portions, and s is thesafety factor. Using a greater safety factor with a particular vesselmaterial, i.e. a particular maximum allowable tensile wall stress, willlead to a greater thickness t for a given operating pressure P.

[0084] For example, for an operating pressure of 0.75 MPa (millionpascals), i.e. about 7.5 atmospheres, an internal radius of 3 inches, asafety factor of 2, and vessel portions 510, 520, 530 comprisingperfluoroalcoxy with a yield strength of 15 MPa, the calculated requiredwall thickness is 0.3 inch. Use of a smaller safety factor, for exampleabout 1, would allow use of a thickness of about 0.15 inch. Where a moreconservative design is desired, a safety factor of 4, for example, wouldgive a required thickness of 0.6″. Greater thicknesses can be used, forexample 1.2 inches or more, however this can add to the cost and weightof the contactor 500.

[0085] Alternatively, the thickness of vessel portions can be derivedempirically, by manufacturing vessels of varying thickness andsubjecting these samples to varying test pressures to determine failurepressure. In some embodiments, the thickness varies at different siteson the vessel. For example, thicker end portions 510, 520 can be used toprovide more stability for gas or liquid line attachments to thecontactor 500.

[0086] Pressure tightness and stability at the joints between theportions 510, 520, 530 can be assisted via use of, for example, gaskets540 and clamps 550 (clamps are indicated only on one side of the vesselin the cross section of FIG. 9).

[0087] The contactor 500 has several advantages over prior packed columncontactors. The stainless steel housing of prior contactors leads to arelatively very heavy and expensive contactor, generally requiring topand bottom steel flanges. Such prior contactors typically incorporate adifficult to manufacture polytetrafluoroethylene liner. In contrast, thecontactor 500 requires few parts, all of which can be produced viarelatively inexpensive injection molding techniques. This can provide apacked column contactor 500 that is more reliable than prior packedcolumn contactors at a cost about 80% less than prior packed columncontactors. Further, via injection molding, liquid or gas lineconnectors 511, 512, 513, 514 can be formed as integral portions of thefirst end portion 510 or the second end portion 520 for a furtherreduction in contactor parts and cost, and increased reliability.

[0088]FIG. 12 shows an embodiment of a contactor 600 of particular usein providing ozonated liquids for semiconductor wet bench processing.The contactor 600 can be used independently of the ozonated watergenerator 1000.

[0089] The contactor 600 includes a tubular portion comprising a housing610 made from a material that is compatible with semiconductorprocessing. A fluoropolymer is preferred, such as perfluoroalcoxy (PFA)to provide compatibility with the presence of hydrofluoric acid. A firstend of the housing 610 is joined in fluid communication with a firstfitting 620. The first fitting is used for connection to a liquid supplyline, for example a DI water supply line or a sulfuric acid supply line.A second end of the housing 610 is joined in fluid communication with asecond fitting 630. The second fitting is used for connection to anozonated liquid supply line. A third fitting 640 is joined in gaseouscommunication with a side of the housing 610 preferably nearer to thefirst fitting 620 than to the second fitting 630. The third fitting 640is used for connection to a gas supply line, the gas comprising ozone.The fittings 620, 630, 640 are made with use of semiconductor processingcompatible components, for example Flaretek® port connections availablefrom Entegris, Inc. (Chaska, Minn.).

[0090] The tubular portion further comprises one or more internal mixingelements 650, some of which are seen, in FIG. 12, in a cut away crosssection of the tubular portion. The elements 650 cause turbulence andmixing of gas that enters the housing 610 via the third fitting 640 andliquid that enters the housing 610 via the first fitting 620. Thismixing helps to provide a relatively high efficiency mass transfer ofozone diffusion into the liquid.

[0091] A variety of turbulence inducing shapes are suitable for theelements 650. Curved shapes are preferred, with an extent along thelength of the housing 610 greater than an internal width of the housing610. An internal width of the housing 610 is about 5 to 30 millimetersand preferably 15 millimeters for typical semiconductor processingapplications.

[0092] In one embodiment, each of the elements 650 has upstream anddownstream ends that are substantially flat and twisted relative to eachother. The symmetry of the twist can alternate, for example fromleft-handed to right-handed corkscrews, from element 650 to element 650along the housing 610. In another embodiment, the symmetry alternates ingroups of elements 650. In another embodiment, the element 650 symmetryalternates randomly.

[0093] The contactor 600 has particular utility in supplying ozonatedliquids to semiconductor processing wet benches. FIG. 13a shows atypical prior art wet bench 1370. A liquid, such as deionized water orsulfuric acid, is delivered to the wet bench 1370 along a liquiddelivery line 1320. Ozone is delivered separately to the wet bench 1370via an ozone delivery line 1310. Ozone bubbles 1340 are injected intoliquid 1330 in the wet bench 1370. As the ozone bubbles 1340 risethrough the liquid 1330, a portion of the ozone diffuses into theliquid, providing an ozonated liquid for treatment of semiconductorwafers residing in the wet bench (not shown).

[0094] In contrast to prior art methods, a wet bench system is shown inFIG. 13b. The contactor 600 receives ozone from a gas supply line 615and liquid from a liquid supply line 612 and delivers ozonated liquid680 to an ozonated liquid delivery line 660 for delivery to a wet bench670. Though ozone bubbles 690 are present in the ozonated liquid 680,the turbulent mixing of liquid and ozone gas prior to delivery to thewet bench 670 has several advantages. The ozonated liquid 680 in the wetbench 670 has an ozone concentration that is more uniform and, ifdesired, greater than in prior art methods. Further, more efficient useis made of ozone gas. Existing wet bench systems of the prior art typecan be readily converted to the type shown in FIG. 13b, largely usingexisting plumbing.

[0095] Provision of ozonated DI water following the principlesillustrated by the embodiment of FIG. 13b has several advantages overuse of ozonated water generators for supply to a wet bench 670. Theembodiment of 13 b is far less expensive and far more reliable. Further,reduced downtime due to a highly reliable ozonated DI water sourcereduces the very high costs typically associated with shutdowns of asemiconductor manufacturing process line. Reduced repairs further add tothe safety of a manufacturing operation.

[0096] In the following, highly pure water, as typically used insemiconductor processing is variously referred to as DI water, water,pure water and ultra-pure water (UPW).

[0097] FIGS. 14-16 illustrate embodiments of apparatus and methods tocontrol ozonated water flow and concentration. FIG. 14 is block diagramof an embodiment of an ozonated water flow and concentration controlunit 1400. The unit 1400 receives ozonated water from an ozonated watergenerator and DI water from a DI water source. After mixing the receivedliquids, the unit 1400 delivers ozonated water of a modified ozoneconcentration and/or flow rate to one or more process tools.

[0098] The unit 1400 can include a DIO3 flow control valve 1410 and/or aDI water flow control valve 1420. The valves 1410, 1420 can be used tocontrol the concentration of ozone in ozonated water exiting the unit1400 by controlling a mix volume ratio of ozonated water from thegenerator and water from the DI water source. The valves 1410, 1420 canalso be used to control the flow rate of output ozonated water.References to DI water are herein understood to encompass highly purewater as commonly used in semiconductor processing.

[0099] The control unit 1400 permits control of ozonated waterconcentration and/or flow rate for one or more process tools while anozonated water generator operates in a steady-state. As described below,use of one or more units 1400 permits a single generator to supply twoor more process tools each with a different concentration of ozonatedwater.

[0100] A “process tool” as used in the present description refers to anypiece of equipment, or portion of a piece of equipment, that utilizesozonated water. For example, separate baths in a single piece ofequipment can be separate process tools.

[0101]FIG. 15 is a block diagram of an embodiment of multiple controlunits 1400, an ozonated water generator 1000, a pure water source 20 andthree process tools 40A, 40B, 40C. The control units 1400 work incooperation with the ozonated water generator 1000 to separately controlthe parameters of ozonated water delivered to the process tools 40A,40B, 40C. Other embodiments include more or fewer process tools, and/oradditional generators 1000.

[0102]FIG. 16 is a block diagram of an embodiment of a generator 1000and a control unit 1400 delivering ozonated water to two process tools40D, 40E. The generator 1000 delivers ozonated water directly to one ofthe process tools 40D, and thus directly controls the concentration ofthe ozonated water that is delivered to the tool 40D. The control unit1400 controls the concentration of ozonated water delivered to thesecond tool 40E.

[0103] Other embodiments vary the number of process tools, and vary thenumber of the process tools that receive ozonated water via one or morecontrol units 1400. Some embodiments include two or more generators1000, for example, to provide a greater quantity of ozonated water.

[0104]FIG. 17 is a detailed block diagram of another embodiment of acontrol unit 1400A, which illustrates one detailed implementation. Thecontrol unit 1400A includes: pneumatic control valves V1, V2; pneumaticshutoff valves V4, V5; a manual adjust valve V3; a flow indicator F1;pressure sensors PR1, PR2; and flow sensors FR1, FR2. The pneumaticvalves V1, V2, V4, V5 are operated using, for example, compressed dryair.

[0105] The control unit 1400A operates as follows. Desired tool processflow rate and ozone concentration are set via a control panel portion ofthe control unit 1400A, or set remotely via computer control. Thecontrol unit 1400A can receive, from an ozone generator, the value ofthe concentration of incoming ozonated water.

[0106] Incoming ozonated water passes through a pneumatic shutoff valveV5, and has its pressure and flow rate measured respectively by apressure sensor PR1 and a flow sensor FR1. Similarly, incoming purewater passes through a pneumatic shutoff valve V2, and has its pressureand flow rate measured respectively by a pressure sensor PR2 and a flowsensor FR2. The two fluids are mixed after passing the flow sensors FR1,FR2, and then pass through a pneumatic valve V1 to exit the control unit1400A.

[0107] The control unit 1400A compares the selected ozone concentrationwith the concentration of the incoming ozonated water, and responsivelyselects a required dilution ratio. The pneumatic valve V2 in the purewater line is adjusted, and the resulting flow rates obtained by theflow sensors FR1, FR2 are compared. Adjustments continue, via a closedloop process, until the flow rates provide the selected dilution ratio.

[0108] The control unit 1400A can also determine the total flow ratemeasured by the flow sensors FR1, FR2, and compare the total to theselected flow rate for the output ozonated water. The pneumatic valve V1near the output port can be adjusted via a closed loop until theselected output flow rate is achieved.

[0109] The manual valve V3 permits, for example, adjustments to obtain adesired level of flow to a drain, as measured via the flow indicator F1.The flow to drain passes through one of the pneumatic shutoff valves V4.Monitoring of the pressure sensors PR1, PR2 can permit emergencyshutoff, if, for example, safe pressure levels are exceeded.

[0110] In one embodiment, the generator 1000 delivers ozonated waterthat is saturated with ozone and a control unit performs mixing underpressure, to avoid out-gassing of the ozone. In one embodiment, incomingsaturated ozonated water passes through a straight input line of uniformdimension.

[0111] Features of the invention can provide numerous benefits, forexample, rapid setting of concentration and flow rate which enables fastramp up and ramp down of the process fluid (allowing optimized processcycles in stop/go mode), and an enlarged flow and concentrationperformance range of a process fluid.

[0112] In illustrative embodiments, a control unit 1400 receivesozonated water having a flow rate in a range of approximately 0 to 35liters/min, and DI water having a flow rate in a range of approximately0 to 42 liters/min. A preferred drain flow is in a range ofapproximately 0 to 2 liters/min. Ozone concentration in output ozonatedwater can be in a range of 0% to 100% of input ozonated waterconcentration. It is herein understood that 0% ozone concentration inoutput ozonated water can be obtained by delivering only DI water to theoutput of a control unit.

[0113] While the invention has been particularly shown and describedwith reference to specific preferred embodiments, it should beunderstood by those skilled in the art that various changes in form anddetail may be made therein without departing from the spirit and scopeof the invention as defined by the appended claims. For example, acontrol unit can be used to control the flow and/or concentrationparameters for two fluids other than ozonated water and/or DI water. Forexample, a control unit can control the mixing of more than two fluids.For example, a control unit can include two or more outputs; each outputcan supply ozonated water having a different concentration.

What is claimed is:
 1. A method for supplying ozonated water to morethan one process tool, comprising: receiving ozonated water having afirst concentration from an ozonated water generator; receiving waterfrom a source; mixing at least one of the received ozonated water andthe received water from the source to produce ozonated water having asecond concentration; and supplying ozonated water having the secondconcentration to a first process tool, while supplying ozonated waterfrom the ozonated water generator to a second process tool.
 2. Themethod of claim 1 wherein supplying ozonated water from the ozonatedwater generator to the second process tool comprises mixing at least oneof ozonated water from the ozonated water generator and water from thesource to produce ozonated water having a third concentration, andsupplying the ozonated water having the third concentration to thesecond process tool.
 3. The method of claim 1 wherein mixing comprisesselecting a ratio of a flow rate of the received ozonated water to aflow rate of the received water from the source to produce the ozonatedwater having a second concentration.
 4. The method of claim 3 whereinmixing further comprises adjusting at least one of the flow rate of thereceived ozonated water and the flow rate of the received water toprovide the selected ratio.
 5. The method of claim 1, further comprisingselecting a flow rate of ozonated water having the second concentration,and controlling a flow rate of the received ozonated water and a flowrate of the received water from the source to produce the selected flowrate of ozonated water having the second concentration.
 6. The method ofclaim 1, wherein mixing comprises mixing substantially none of thereceived ozonated water with the received water from the source toprovide the second concentration substantially equal to 0% ozoneconcentration.
 7. A method of supplying ozonated water to more than oneprocess tool, comprising: providing an ozonated water control unitcomprising: an ozonated water input port for receiving ozonated waterhaving a first concentration from an ozonated water generator; a waterinput port for receiving water from a source; an ozonated water outputport in fluid communication with the ozonated water input port and thewater input port; and a valve for controlling a flow rate of water inthe water input port to produce ozonated water having a secondconcentration in the output port, in cooperation with a flow rate ofozonated water in the ozonated water input port, and supplying ozonatedwater having the second concentration from the output port to a firstprocess tool, while supplying ozonated water from the ozonated watergenerator to a second process tool.
 8. The method of claim 7 whereinsupplying ozonated water from the ozonated water generator to a secondprocess tool comprises providing a second ozonated water control unitcomprising: an ozonated water input port for receiving ozonated waterhaving the first concentration from the ozonated water generator; awater input port for receiving water from the source; an ozonated wateroutput line in fluid communication with the ozonated water input portand the water input port; and a valve for controlling a flow rate ofwater in the water input port to produce ozonated water having a thirdconcentration in the output port, in cooperation with a flow rate ofozonated water in the ozonated water input port, and supplying ozonatedwater having the third concentration from the output port to the secondprocess tool.
 9. A ozonated water control unit comprising: an ozonatedwater input port for receiving ozonated water having a firstconcentration from an ozonated water generator; a water input port forreceiving water from a source; an ozonated water output port in fluidcommunication with the ozonated water input port and the water inputport; and a valve for controlling a flow rate of water in the waterinput port to produce ozonated water having a second concentration inthe output port, in cooperation with a flow rate of ozonated water inthe ozonated water input port.
 10. The ozonated water control unit ofclaim 9, further comprising a flow sensor for measuring the flow rate ofwater in the water input port, wherein the valve is adjusted in responseto the measured flow rate to obtain a selected flow rate to produce theozonated water having a second concentration.
 11. The ozonated watercontrol unit of claim 10, further comprising a flow sensor for measuringthe flow rate of the received ozonated water in the ozonated water inputport, and a valve for controlling a flow rate of the received ozonatedwater in the ozonated water input port, wherein the valve forcontrolling the flow rate of the received ozonated water is adjustedresponsively to the measured flow rate of the received ozonated water toprovide a selected ratio of the flow rate of the received ozonated waterto the flow rate of the received water from the source.
 12. The ozonatedwater control unit of claim 10, further comprising a second ozonatedwater output port in fluid communication with the ozonated water inputport and the water input port, the second ozonated water output port forsupplying ozonated water having a third concentration.
 13. The ozonatedwater control unit of claim 10, wherein the second concentration is in arange of 0% to 100% of the first concentration.
 14. A ozonated watersupply system, comprising: an ozonated water generator; a first ozonatedwater control unit in fluid communication with the ozonated watergenerator, the control unit comprising: an ozonated water input port forreceiving ozonated water having a first concentration from the ozonatedwater generator; a water input port for receiving water from a source;an ozonated water output port in fluid communication with the ozonatedwater input port and the water input port; and a valve for controlling aflow rate of water in the water input port to produce ozonated waterhaving a second concentration in the output port, in cooperation with aflow rate of ozonated water in the ozonated water input port, and asecond ozonated water control unit in fluid communication with theozonated water generator for supplying ozonated water having a thirdconcentration to a second process tool while supplying ozonated waterhaving the second concentration to a first process tool.